derek bailey wrote:home made add on on a .22 rf so 100yards ive got a carls custom t20 at te moment

If it hasn't already got one then a bog standard Chinese AS type pill for your T20 would most likely do you. They are available from every man and his dog for about £12

If you want something better then our Black Sun 2 pill for the T20 would be a good choice and if you want absolute maximum range (hundreds of yards) and or perfect image the the Black Sun Ruby pill would be the one to go for.